Continuously loaded communication conductor



Oct. 11, 1932. 'J. .J. swam-r 1,381,480

CQNTINUOUSLY LOADED COMMUNICATION CONDUCTOR Filed April 10, 19 29 lNV/E'N TOR J J GILBERT JOHN J. GILBERT, OF DOUGLASTON, NEW YORK, ASSIGrNORv TO BELL TELEPHONE LABORA Patented Oct. 11, 1932 UNITED STATES P TE T OFFICE.

TORIES, INCORPORATED, OF NEWYORK, N. Y.,-A CORPORATION OF NEW YORK coNrmuous' Y oner communioarron CONDUCTOR Appll'cation fileanprn 1o,

loaded communication conductors, and more specifically to continuously "loaded sub marine telegraph or telephone cables in which the loading material is applied to the ';which is parallel to the conductor and which is due 'tothe pitch of the helix to which the tape is applied. This component of the flux conductor in the form of a thin tape or strip.

In cables of this type it has been the practice to apply the loading material in the form of a comparatively narrow tape and to wind it in one or more layers about the centralconductor, each layer constituting a contlnuous helix wound with the edges of -adjacent turns abutting as closely as practicable.

An object of the present invention is to reduce the eddy-current losses in the loading material inlong cables for'high frequency telegraphy or for telephone communication.

Another object of the invention is to reduce the component of the flux in the loading material which is parallel with the conductor in order to secure higher transmission efiiciency. 7

Another object is to provide a loading which may be applied at low cost and with small chance of breakage. 1

Other objectswhich may be attained will be apparent from the following description.

To attain these objects the continuous loading for a communication conductor in accordance with the invention is composed of one or more tapes of magnetic material which are applied in a layer of helical turns with a con-- siderable amount of overlap between adjacent turns. The loading materlal may be "of any desired magnetic material such as iron or alloys of iron and nickel with or without cobalt, which may be found to be particularly suited for thispurpose. Y

It has been found in the past that the eddy current losses, even in the most eflicient load-- ing materials, reach considerable values frequencies such as occur in telephone cables and may be quite appreciable in high speed telegraph cables. The

thicknessof the tape, of course, has been rebetter grade loading materials have comparatively high resistance,

1929. Serial No 353,994.

duced to a fraction of the total thickness of the layer.

Experience has also shown that it is desirable under "certain circumstances to reduce to a minimum the component ofthe flux increases with the pitch and for agiven size of conductor it therefore increases withthe width of the loading tape. It has therefore been found desirable to reduce the width of thetape as much asmechanical requirements would permit.

It is'thus'apparent that both of the conditions just referredto-would require reduction to a minimum of the dimensions of the tape. "However,-the limit of reduction is deing it about the conductor. 7

In the modern winding machine the taping head revolves with 1 a very high speed in order that the output of the machine may beas large as possible. The chances of breakage of the tape therefore are quite large. 'It has been customary to-produCe tape as thin as 2 mils and of a width of about 20 to 30 mils. If the tape be further reduced in dimensions the speed of the winding head must be reducedor else the operation of the machine will be much more frequently interrupted due to breaking of the loading The present invention offers an opportunity'to improve theseconditions. 4 I

In" order to facilitate the understanding comprises a central conductor 10 which may ftermined by the strain under which the a tape is placed during the operation of windbe of any desired construction. A preferred form isshown in the drawing and comprises a-solid core surrounded by a plurality of segmental strips formed to fit snugly about the core. About this conductoris placed a layer of loading material 11 shown partly insection. This layer consists of magnetic material formed into tape and wound heliproximately four times the thickness of the, tape. The layer is shown assbeingcomposed of a single helix consisting of a single continuous tape wound in such a manner that each turn overlaps three=fourths=of the-Width of itsv predecessor. This overlap may be-increased or decreased inaccordance with the requirements. It is als possibleto' wind the loading as a double, treble orquadruple V helix by winding two, three, or four different tapes. about the conductor in: a simultaneous operation, in Which case adjacent overlapping turns would beformed by -different tapes.

The-loading material is surrounded by an insulating envelope-l2, the! dimensions and ""lnaterial of NVhlCll'iS determined by the cone ditions under which the cable is to be used. Theicable may further be provided with armoring'or other protecting layers which, hQWever, have not been shown 1n the-draw- "ing since they form no part of this -1nvention. V

Upon an examination of the drawingit will be noted that with the embodiment shown the ,width of the tape is four times. the pitch of "eachfturm'so thatit isyapparent that itis possible in accordance with Y the present in-.

vention for a given pitch to increase the width oflthe tape beyond the pitch orelseito reduce the .pitch for a -given Width oftape, 'this, in

strength of the tape orelse to reduce the flux component whichis parallel to the conductor, or both. The increase in widthofthe tape, which may be obtained :bythis; arrange.- ment, would permit a decrease in thickness of..

thetape without loss of mechanicalstrength;

which would result in a reduction of the eddycurrent losses.

1,, Thus, if in the case illustrated it be desired.

"toprovideia layer of loading. 5 to 6 mils; in

thickness. a tape l mil-in thickness maybe. used with a three-quarter overlap to form-,in eilect, four layers; and if a pitch of 6 milsb-e' desired'the-width of the tape would be 24 mils. The cross-sectional area ofth-is tape wouldbe'24 sqrmils, considering acase in accordance with the prior art using atape of a thickness of 2 mils and a would also be 24. sq. milsand the tensile strength would be the same as of the tape describedabove. The loading layer in the lat ter case-would be formed of 2 separate tapesandthe, thickness of the tape-2 mils, in the first casethe pitch wouldbe reduced by onehalfto 6 mils andthe'thicknes's of the tape also to one-half or 1 mil. -The-result.of are to satisfy-the optimum requirements of the three factors eddy-current losses,- parallel flux component and mechanical strength.

What isclaimedis:

1..In a. continuously loaded communication conductor, a magnetic material surrounding the conductor and comprising a layer of helical turnsof tape with not less than about i 50 overlap of adj acent; turns 2; A. continuously loaded signaling conductor comprising a magnetic tape of :magneti'c'material wound about said conductor-in helical turns of not-less than ab0ut.50% overlap of-adjacent turns.

3.-. A continuously loaded submarine cable comprising'a central conductor, a layer of loadin-g material about said conductor having. eddy-current losses reduced therein. gb-y being formed into an effective multiplellayer,

said loading material being of a magnetic material formed into avery thin tape and wound in'helical turns about said conductor with suflicientoverlap of adjacent turns to pro-- duce the: desired thicknessof said multiple layer.- and an insulating envelope about said I layen. order to either increase the' mechanicab? 5. A method of producing {a continuously loaded signaling conductor whereby the eddycurrentdosses in the-loading (may be reduced u;

l which comprises forming theloading material. into very thin tape, and: winding said .tap e;he1ically,about {the conductor with sulfa cient overlapiof adjacent; turns to. produce a layeriof loading ofthe. desired thickness.

,6:-;A method. in accordancewith claim, 5. in which thelayer of loading is formed by, windi'ng a. single continuous tape about the conductor-with overlapping helical turns.-

. 7 A continuously loaded signaling conduca tor having a metallic core loaded-with a tape, of. magneticmaterial having a thickness not width of 12 mils, the. cross-sectional area in excessof 2 mils, said tape being helically wound directlyupon the core in conductive pingiof the adjacent turns for producing a inexcess of-Q mils, said tape beingwound helically; upon said core 1n 1 conductive rela? 1 predetermined inductive load perzunit length wound in an inner and an outer layer; Whereasin the latter casethe-pi-tch' wouldbe12 mils y 9 4.;A submarine-cable in accordance: with tion thereto with an overlap of substantially one-half the Width of the loading tape for predetermining the inductance of said conductor per unit length thereof.

In Witness whereof, I hereunto subscribe my name this 8th day of April, 1929.

JOHN J. GILBERT. 

